Disk drives comprise a disk that includes data tracks with physical sectors for storing host data, where the physical sectors have a particular size, such as a 512 byte or a 4 kilobyte (4 KB) size. Traditionally, the host transfers data to the disk drive in logical block address (LBA) size units that are equal in size to the physical sectors on the disk. However, in a disparate sector size environment, where the host LBA size is smaller than the disk drive physical sector size, the host can issue a write command with less than a full physical sector amount of data. Since the disk drive can only read or write whole physical sectors, a read-modify-write operation is performed to update the physical sector with the host provided data while preserving existing data not provided with the current host write command.
However, if an uncorrectable error, such as an uncorrectable error correcting code (ECC) error, occurs during the read portion of the read-modify-write operation, the stored data in the physical sector cannot be read. As a result, the physical sector is typically written with a combination of valid data provided by the host write command and fill data, which is invalid data that can be read. Although the physical sector can now be read, not all of the LBAs in the physical sector correspond to valid host data. Thus, when the host subsequently issues a command requesting data stored in the physical sector, the disk drive must avoid transferring invalid data to the host.